Devices for utilizing the thermal expansion of wax



Dec. 10, 1957 J. F. SHERWOOD 2,815,642

DEVICES FOR UTILIZING THE THERMAL EXPANSION OF WAX Filed Oct. 21, 1955 .37 II Z? I. a? I 3? INVENTOR.

Join fJbern/oao B Y I United States Patent FOR UTILIZING THE THERMAL EXPANSION OF WAX DEVICES This invention relates to an activating device for actuating any desired reciprocating or oscillating element in consequence of variations in electrical current. The principal object of the invention is to provide a small, compact unit which will operate from the small, exceedingly powerful thermal expansion of a wax to produce hydraulic actuating pressure, and which can be minutely and accurately controlled by control of an electrical current supply.

The invention has many uses, one of which is to operate flue dampers and fuel valves from thermostatic controls in industrial and domestic heating plants.

Other objects and advantages reside in the detail construction of the invention, which is designed for simplicity, economy, and efliciency. These will become more apparent from the following description.

In the following detailed description of the invention, reference is had to the accompanying drawing which forms a part hereof. Like numerals refer to like parts in all views of the drawing and throughout the description.

In the drawing:

Fig. l is a side view of the improved actuating mechanrsm;

Fig. 2 is a longitutinal section therethrough, taken on the center line of Fig. 1;

Figs. 3, 4, and are cross-sectional views, taken on the lines 3-3, 4-4 and 5-5, respectively, Fig. 2; and F Fig. 6 is an end view looking toward the right end in The improved actuating device comprises a hydraulic pump cylinder 10 provided with any suitable supporting bracket 11 and formed with a closed extremity 12 and an open extremity surrounded by a peripheral flange 13. A hydraulic power cylinder 14 is mounted in axial alignment with the pump cylinder 10 and secured to the latter through the medium of a second peripheral flange 15 and suitable attachment screws 16. A port 30 communicates between the cylinders 10 and 14. The hydraulic power cylinder 14 is relatively longer and relatively smaller in diameter than the pump cylinder 10.

The closed extremity 12 of the pump cylinder is formed with an attachment flange 17 to which an attachment flange 19 of a wax chamber member 18 is secured by means of suitable attachment screws 20. The wax chamber member 18 is preferably provided with heat radiating fins 40. A head disc 21 is secured to the wax chamber member 18 through the medium of suitable attachment screws 22.

An actuating rod 23 extends axially through the power cylinder 14 and terminates, at its inner extremity, within the cylinder 14 in a power piston 24. The actuating rod extends through a cylinder head plug 25 threaded or otherwise secured in the extremity of the cylinder 14. The outer extremity of the actuating rod is provided with any suitable means for attaching the rod to the mechanism to be actuated. As illustrated, the means comprise a clevis 27 threaded onto the rod 23 and locked in place thereon by means of a suitable jam nut 28.

A compression spring 29 is compressed between the head plug 25 and the piston 24 and surrounds the rod 23 within the cylinder 14 to constantly urge the piston 24 toward the port 30. The pump cylinder 10 is provided with a floating pump piston 31 which is constantly urged away from the port 30 by means of a return spring 32.

The pump piston 31 is forced against the action of the spring 32 by means of a plunger 33 provided at its inner extremity with'a plunger head 34 which contacts the piston 31'. 'In use,'the entire open space between the pump piston 31 and ,the power piston 24 is filled with suitable hydraulic fluid. t

The outer extremity of the plunger 33 extends into a high-pressure cylinder 35 concentrically embedded in the flange 17 and the flange 19 across the contacting plane of the two flanges. The high-pressure cylinder 35 is formed of a metal having high tensile strength, such as steel, and opens to the inner extremity of a wax chamber 36 completely filled with a suitable thermal expansible wax, such as paraflin. The outer extremity of the wax chamber is closed by means of an insulating gasket member 37 which forms the support for an electrical heating filament 38 which is embedded in the wax. The gasket also forms a support for electrical terminals 39 for conducting electrical current to the filament 38.

Let us assume that the device is being used to control the flue damper of a heater in consequence of electrical variations in a thermostat circuit connected to the electrical terminals 39 and that the clevis 27 is connected to the flue damper so that when the mechanism is in the position of Fig. 2 the damper will be open. As the temperature rises, the flow of current through the filament 38 increases, causing the latter to heat the wax in the wax chamber 36. This causes a thermal expansion of the wax so that the latter will exert pressure on the extremity of the plunger 33 to force the latter inwardly in the high-pressure cylinder 35 so that the plunger head will force the pump piston 31 against the hydraulic fluid in the pump cylinder 10.

The hydraulic fluid will be forced under pressure through the port 30 into the power cylinder 14 against the power piston 24 to force the latter against the action of the spring 29 and transmit movement to the clevis 27 to move the damper toward the closed position.

If the flow of electrical current is increased, the expansion of the wax will be increased, and the movement of the actuating rod will continue. Should the electrical current be reduced to a pre-determined point, the expansion of the wax will cease and should the current be cut 01f, the Wax will immediately thermally contract, the dissipation of heat being assisted by the radiating fins 40, to allow the plunger 33 to move into the high-pressure cylinder 35 under the urge of the spring 32 and under the urge of the compression imparted to the hydraulic fluid in the pump cylinder 10 by the spring 29.

While a specific form of the improvement has been described and illustrated herein, it is desired to be understood that the same may be varied, within the scope of the appended claim, without departing from the spirit of the invention.

Having thus described the invention, what is claimed and desired secured by Letters Patent is:

A device for imparting a reciprocal movement to a mechanism comprising: a power cylinder; a power piston in said power cylinder; a piston rod extending from said power piston and adapted to be connected to the mechanism to be actuated; a pump cylinder mounted on said power cylinder in communication with the latter through the medium of hydraulic fluid; resilient means urging said power piston against said hydraulic fluid; a pump piston reciprocally mounted in said pump cylinder; spring means urging said pump piston in one direction; a high-pressure cylinder supported from and in axial alignment with said Patented Dec. 10, 1957 pump cylinder; a plunger in said high-pressure cylinder extending into contact with said pump piston so as to urge said pump piston in the other direction; a wax chamber communicating with said high pressure cylinder; wax completely filling said wax chamber, so that thermal expansion of said wax will cause the latter to act against the plunger to cause the latter to exert pressure against said hydraulic fluid, and a thermostatically controlled electrical heating element positioned within said wax-chamber and embedded in the wax therein. 10

References Cited in the file of this patent UNITED STATES PATENTS 861,310 Nolen July so, 1901 15 4 Fulton Apr. 15, 1919 Houplain June 28, 1932 Mulvey Mar. 13, 1934 Webb Mar. 22, 1938 Platzner Sept. 17, 1940 Vernet Jan. 30, 1945 Kempton Nov. 29, 1949 Molotzak Tune 20, 1950 Ray .....J........ Oct. 23, 1951 

